1. Field of the Invention
The present invention relates to a control system of a self propelled industrial machine like a forklift.
2. Description of the Related Art
A self propelled industrial machine such as a forklift and a truck crane works to lift or move an object. Such a self propelled industrial machine is different from an automobile, and severe conditions are required in driving operations. In the self propelled industrial machine, it is required that an operator carries out a machine work control operation and a running control operation, while confirming the loaded object, a road and a working place, and a running state of the industrial machine. Thus, control operations other than the running control operation are required in consideration of conditions such as an operator posture of the operator.
A self propelled vehicle body of the self propelled industrial machine does not have a cover in any portion other than a driving seat, and the operator sometimes stands up from the seat and moreover leaves the seat to check a working environment or a machine element.
A conventional safety mechanism to protect the operator who leaves the driving seat is known in Japanese Laid Open Patent Application (JP-A-Heisei 64-13398). In this conventional example, a seat switch is arranged in the seat in a forklift, and the drive state of a motor is controlled based on the seat switch.
As conventional running control techniques, an electric control system is known in which solenoids are operated in accordance with electric switches to control a drive section. In addition, a mechanical control system is known in which a control valve is controlled through the drive of a hydraulic pressure unit which is mechanically connected with a lever handle. In the self propelled industrial machine, it is required to cope with any trouble of the electric control system. Also, in the self propelled industrial machine, the operator is required to carry out various machine control operations. Therefore, automation of the running control and safety control are especially required.
Also, in the self propelled industrial machine, a phenomenon known as creep occurs, in which a part of the engine torque is transferred to a transmission so that the self propelled industrial machine runs when a forward direction movement switch is in a neutral position in an idling state.
A conventional running control technique for restraining the creep phenomenon is known in Japanese Laid Open Patent Application (JP-P2002-181186A). In this conventional example, a neutral control section carries out a neutral control to keep a friction coupling element to a sliding state when an automatic transmission is in a running range and a predetermined condition is satisfied. When the neutral state is cancelled through generation of the velocity of a car, the neutral control section prohibits the neutral control until an acceleration pedal is footed.
Also, a running control technique for restraining the creep phenomenon in relation with vehicle velocity is known in Japanese Laid Open Patent Application (JP-A-Heisei 11-193866). In the conventional example, a neutral control unit sets an automatic transmission to a neutral state when predetermined conditions are satisfied even if the shift range of the automatic transmission is in a forward direction running range. The conditions are as follows: (a) an acceleration opening is smaller than a predetermined value, (b) a brake is footed, (c) a downshift is carried out, and (d) a velocity is smaller than a predetermined velocity. When all the conditions are satisfied, the automatic transmission is set to the neutral state.